Display device having common electrode corresponding to a specific pixel electrode in which the area thereof is smaller than the area of other adjoining pixel electrodes and in which that common electrode has a bridging connection

ABSTRACT

The present invention is intended to control the color temperature of white exhibited by a liquid crystal display device. White is produced when light waves emitted through pixels associated with three colors of red, green, and blue have maximum intensities. The amounts of light emitted through the respective pixels are controlled by differentiating the shapes of the pixel electrodes disposed at the respective pixels from one another. Thus, the color temperature of white is controlled. Otherwise, the shapes of interceptive films disposed at the respective pixels are differentiated from one another in order to control light waves emitted through the respective pixels. Thus, the color temperature of white is controlled. The interceptive film may be shaped like the pixel electrode. Otherwise, the interceptive film may be realized with an interceptive pattern other than that of the pixel electrode or one of openings bored in a black matrix.

CLAIM OF PRIORITY

The present application claims priority from Japanese Application JP2005-197770 filed on Jul. 6, 2005, the content of which is herebyincorporated by reference into this application.

FIELD OF THE INVENTION

The present invention relates to a display device, or more particularly,to a technology that will be effectively applied to a liquid crystaldisplay device having a liquid crystal display panel that includes pixellocations associated with three primary colors of red, green, and blue.

BACKGROUND OF THE INVENTION

Conventionally, display devices include a liquid crystal display devicethat has a liquid crystal display panel and that can achieve colordisplay. In recent years, the liquid crystal display device capable ofachieving color display has been widely adapted to a liquid crystaltelevision, a liquid crystal display for personal computers, or adisplay of a personal digital assistant (PDA) or portable cellularphone.

The liquid crystal display panel for color display (hereinafter called acolor liquid crystal panel) is a display panel having a liquid crystalmaterial sealed in a space between a first substrate (TFT substrate) inwhich thin-file transistors (TFTs) and pixel electrodes are set inarray, and a second substrate (color filter substrate) in which colorfilters of red, green, and blue are disposed so that the color filterswill be opposed to the respective pixel electrodes. At this time, onedot (display pixel) displayed on the color liquid crystal panel isproduced by one set of a red pixel location at which a red color filteris disposed, a green pixel location at which a green color filter isdisposed, and a blue pixel location at which a blue color filter isdisposed.

A color liquid crystal display panel in which pixel electrodes aredisposed at respective pixel locations and oriented in plural directionsfor the purpose of improvement of a viewing angle has been proposed(refer to, for example, U.S. Pat. No. 6,256,081).

SUMMARY OF THE INVENTION

In conventional liquid crystal display devices, generally, the areas offields at the red, green, and blue pixels respectively through whichlight passes are identical to one another. Gray levels to be expressedat respective pixels are controlled independently of one another inorder to render various tones.

At this time, white exhibiting a maximum luminance is produced bysynthesizing a maximum-luminance shade of red, a maximum-luminance shadeof green, and a maximum-luminance shade of blue. The degree of white(for example, reddish white or bluish white) is represented by an indexcalled a color temperature. The color temperature is determined by thebalance of luminance values of red, green, and blue respectively. Thecolor temperature directly affects how an image is seen. The colortemperature is therefore requested to be highly precisely set to apredetermined value, which is determined as a specification, accordingto the purpose of use of a product or a consumer's request.

Consequently, many products that exhibit nearly the same characteristicsbut exhibit different color temperature values must be manufactured. Ifthe specification of the color temperature and the size of a product areassociated with each other on a one-to-one correspondence basis, theproduct can be easily checked for the color temperature. However, pluralspecifications of color temperatures may be associated with the sameproduct size. In this case, if panels that are different from oneanother in terms of the specification of the color temperature come tocoexist in the course of manufacture because of a trouble occurring in amanufacture control computer, the coexisting panels may become hard toidentify.

One object of the present invention is to provide a display devicehaving a color temperature thereof adjusted highly precisely.

Another object of the present invention is to provide a display devicewhose specification of a color temperature can be readily identified.

The above objects and other objects of the present invention and thenovel features thereof will be apparent from the description of thepresent specification and the appended drawings.

The present invention disclosed in the present application will beoutlined below.

-   -   (1) In a display device including pixel locations (hereinafter        pixels) associated with a first color, pixels associated with a        second color, and pixels associated with a third color, any of        the three kinds of pixels is a specific pixel at which a        metallic pattern whose shape is different from that of a        metallic pattern formed at each of the other pixels is formed.    -   (2) In the display device set forth in (1), the metallic pattern        is separated from the other metallic patterns on a planar basis.    -   (3) In the display device set forth in (1), a pixel electrode        disposed at the specific pixel is smaller than the pixel        electrode disposed at each of the other pixels.    -   (4) In the display device set forth in (3), the shape of the        pixel electrode disposed at the specific pixel is different from        the shape of the pixel electrode disposed at each of the other        pixels because the pixel electrode at the specific pixel becomes        smaller due to the metallic pattern.    -   (5) In the display device set forth in any of (1) to (3), common        electrodes are superimposed on the respective pixel electrodes        on a planar basis. Each of the pixel electrodes includes        openings, and the openings bored in a smaller pixel electrode is        smaller than those bored in the pixel electrode disposed at each        of the other pixels.    -   (6) In the display device set forth in (4), common electrodes        are formed on a planar basis to be superimposed on the        respective pixel electrodes. A bridging connection is applied to        the metallic pattern in order to connect the common electrode to        the common electrode at an adjoining pixel.    -   (7) A display device includes first pixels at each of which a        first color filter is disposed, second pixels at each of which a        second color filter is disposed, and third pixels at each of        which a third color filter is disposed. At each of the pixels, a        pixel electrode is opposed to the color filter. The pixel        electrode has plural slits. The area of the pixel electrode at        the first pixel defined by the perimeter of the pixel electrode        is smaller than the area of the pixel electrode at the second        pixel defined by the perimeter of the pixel electrode.    -   (8) In the display device set forth in (7), an area by which a        metallic layer is bared at the first pixel is larger than an        area by which the metallic layer is bared at the second pixel.    -   (9) In the display device set forth in (7) or (8), common        electrodes are superimposed on the respective pixel electrodes        on a planar basis. Each of the common electrodes is formed on a        planar basis to be exposed through the slits in the pixel        electrode. A total area occupied by the slits in the pixel        electrode disposed at the first pixel is smaller than a total        area occupied by the slits in the pixel electrode disposed at        the second pixel.    -   (10) In the display device set forth in any of (7) to (9), the        positions of the slits in the pixel electrode at the first pixel        are different from the positions of the slits in the pixel        electrode at the second pixel.    -   (11) In the display device set forth in any of (7) to (9), the        number of slits formed in the pixel electrode at the first pixel        is smaller than the number of slits formed in the pixel        electrode at the second pixel.    -   (12) In the display device set forth in any of (7) to (9), the        width of the slits in the pixel electrode at the first pixel is        smaller than the width of the slits in the pixel electrode at        the second pixel.    -   (13) In the display device set forth in any of (7) to (9), the        spacing between adjoining one of the slits in the pixel        electrode at the first pixel is wider than the spacing between        adjoining ones of the slits in the pixel electrode at the second        pixel.    -   (14) In the display device set forth in any of (7) to (9), the        angle of the slits in the pixel electrode at the first pixel is        different from the angle of the slits in the pixel electrode at        the second pixel.

Owing to the structure like the one of the implement (1), the displaydevice in accordance with the present invention controls the balanceamong amounts of light emitted through pixels associated with differentcolors. At this time, the shape of the metallic pattern can beaccurately controlled through photo-fabrication. Consequently, the colortemperature can be accurately controlled.

Moreover, since a characteristic metallic pattern is left bared on thepixel, the specification of the color temperature can be readilydistinguished by checking the color associated with the pixel at whichthe metallic pattern is left bared.

Moreover, if the patterns are separated from one another on a planarbasis as they are in the implement (2), the specification can be readilydistinguished. In particular, automatic decision making can be achievedthrough pattern recognition.

Moreover, if the metallic pattern is disposed at a pixel whose pixelelectrode is smaller in the same manner as it is in the implement (4),the metallic pattern can be further used for another object. Effectiveuse of an area can be achieved. An example is introduced as theimplement (6). Consequently, image quality can be improved.

If the structure like the one employed in the implement (5) is adopted,a capacitor is formed between the pixel electrode and common electrode.The capacitances of the capacitors formed at the respective pixelsshould preferably be equal to one another. This is intended to prevent avariance in the efficiency in writing data in a TFT among the pixels.The capacitance of the capacitor formed at a pixel at which a smallpixel electrode is disposed is smaller than the capacitance of thecapacitor formed at each of the other pixels. Therefore, openings areformed in the pixel electrode, so that an area occupied by the openingsformed at the pixel at which the small pixel electrode is disposed issmaller than an area occupied by the openings formed at each of theother pixels. Consequently, a difference in the area of a pixelelectrode between one pixel and the other pixels can be reduced, and adifference in the capacitance can be reduced.

The implement (7) is a concrete example of the display device having thestructure like the one of any of the implements (1) to (4), and providesthe same advantages as the implement (1) .

The implement (9) is a concrete example of the display device having thestructure like the one of the implement (5), and provides the sameadvantages as the implement (5).

The implement (9) may be realized by one of the implements (10) to (14)or a combination thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing an example of a display panel employed ina display device in accordance with the present invention;

FIG. 2 is an A-A′ cross-sectional view of the display panel shown inFIG. 1;

FIG. 3 shows an example of pixels included in the display panel employedin the display device in accordance with the present invention;

FIG. 4 shows an example of pixels included in the display panel employedin the display device in accordance with the present invention;

FIG. 5 shows an example of pixels included in the display panel employedin the display device in accordance with the present invention;

FIG. 6 is a B-B′ cross-sectional view of the display panel shown in FIG.5;

FIG. 7 is a C-C′ cross-sectional view of the display panel shown in FIG.5;

FIG. 8 is a D-D′ cross-sectional view of the display panel shown in FIG.5;

FIG. 9 shows an example of pixels included in the display panel employedin the display device in accordance with the present invention;

FIG. 10 shows an example of pixels included in the display panelemployed in the display device in accordance with the present invention;

FIG. 11 shows an example of pixels included in the display panelemployed in the display device in accordance with the present invention;

FIG. 12 shows an example of pixels included in the display panelemployed in the display device in accordance with the present invention;

FIG. 13 shows an example of pixels included in the display panelemployed in the display device in accordance with the present invention;

FIG. 14 is a partially enlarged explanatory view of the display panelshown in FIG. 13;

FIG. 15 shows an example of pixels included in the display panelemployed in the display device in accordance with the present invention;

FIG. 16 shows an example of pixels included in the display panelemployed in the display device in accordance with the present invention;

FIG. 17 is an illustrative explanatory diagram of a variant; and

FIG. 18 is an illustrative explanatory diagram of a variant.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, the present invention will be describedbelow.

In the drawings, the same reference numerals are assigned to componentshaving the same capabilities. An iterative description of the componentswill be omitted.

First Embodiment

A liquid crystal display device will be described below as an example ofa display device.

FIG. 1 is an illustrative plan view showing the outline structure of aliquid crystal display panel, and FIG. 2 is an A-A′ cross-sectional viewof the display panel shown in FIG. 1.

The liquid crystal display device includes a liquid crystal displaypanel that has, as shown in FIG. 1 and FIG. 2, a first substrate 1 and asecond substrate 2 bonded using, for example, an annular sealing member3, and that has a liquid crystal material 4 sealed in the space definedby the substrates 1 and 2 and the sealing member 3. The liquid crystaldisplay device includes, aside from the liquid crystal display panel,for example, a light source (backlight unit), a circuit board on which atiming controller that controls display on the liquid crystal displaypanel and other circuits are mounted, and a semiconductor package suchas a tape carrier package (TCP), in which a driver IC for driving theliquid crystal display panel is encapsulated, or a package manufacturedaccording to a chip-on-film (COF) technique.

For the sake of explanation, the first substrate 1 shall be a TFTsubstrate having TFTs and pixel electrodes set in array, and the secondsubstrate shall be a color filter substrate.

FIG. 3 is an illustrative plan view showing an example of the structureof the TFT substrate 1. In the TFT substrate 1, a pixel zone is definedby gate lines 102 and drain lines 107. A signal sent over the drain lineis applied to each pixel electrode 110 via a TFT.

In FIG. 3, R denotes red, G denotes green, and B denotes blue. Moreover,R, G, and B indicate the colors with which pixels in the TFT substrate 1are associated when the color filter substrate 2 is put on the TFTsubstrate 1.

Referring to FIG. 3, a metallic pattern 500 is disposed at each redpixel as an example. In this case, since an amount of light emittedthrough the red pixel decreases, white produced as the balance of red,green, and blue is adjusted to be bluish. Since the metallic pattern 500is formed in the course of manufacturing the TFT substrate, the shapethereof can be highly precisely controlled through photo-fabrication.Moreover, since a metallic material is employed, compared with theemployment of a transparent material or an organic film, a variance indimensions resulting from etching is reduced. The shape of the metallicpattern can be highly precisely controlled. Consequently, the colortemperature can be highly precisely controlled.

Moreover, since the metallic pattern 500 is directly formed at eachpixel associated with a color that is visualized with a small amount ofemitted light, the specification of the color temperature of the panelcan be directly distinguished.

Before the TFT substrate is united with the color filter substrate 2,since with what colors the pixels are associated are uniquely determinedin the stage of designing, the colors with which the pixels areassociated can be directly distinguished. In this case, the color withwhich a pixel is associated can be more easily distinguished by checkingneighboring pixels.

FIG. 4 shows an example in which a metallic pattern 501 is formed ateach green pixel. The shape of the metallic pattern 501 is differentfrom that of the metallic pattern 500 formed at each red pixel.Consequently, the color temperature can be finely adjusted. In FIG. 4,the position of the metallic pattern 501 in the pixel zone is differentfrom the position of the metallic pattern 500 therein. This is intendedto make it easier to distinguish the specification through patternrecognition. The positions of the metallic patterns are deviated fromeach other horizontally, vertically, or both horizontally andvertically.

FIG. 5 shows another example of the structure of the TFT substrate 1.FIG. 6 shows a B-B′ cross section of the TFT substrate 1 and FIG. 7shows a C-C′ cross section thereof. In the TFT substrate 1 shown in FIG.5 to FIG. 7, gate lines 102, common electrodes 103, and common signallines 104 a are formed on a transparent substrate 101 such as a glasssubstrate. Moreover, an amorphous silicon film 106, drain lines 107, andsource electrodes 108 are formed on the layer over the gate lines 102and common electrodes 103 via a first insulating film 105. Each TFT isrealized with each gate line 102, the first insulating film 105, theamorphous silicon film 106, each drain line 107, and each sourceelectrode 108.

Pixel electrodes 110 are formed on the layer over the drain lines 107and source electrodes 108 via a second insulating film 109. The pixelelectrodes 110 are, as shown in FIG. 6, connected to the respectivesource electrodes 108 by way of respective through holes, for example.Moreover, slits 110 s extending in a first direction are formed in theupper part of each of the pixel electrodes 110 with the center of eachpixel electrode in the extending direction of the drain lines 107. Slits110 s extending in a second direction are formed in the lower half ofeach pixel electrode. Needless to say, the slits 110 s may be extendedin one direction. Moreover, an alignment film 111 is formed over thesecond insulating film 109 and pixel electrodes 110.

FIG. 8 shows a D-D′ cross section of the TFT substrate shown in FIG. 5.Sheet polarizers 6 and 7 are formed on the backs of the TFT substrate 1and color filter substrate 2 respectively, that is, the sides thereofopposite to the liquid crystal layer 4.

The color filter substrate 2 has, for example, as shown in FIG. 6 toFIG. 8, color filters 202 formed on a transparent substrate 201 such asa glass substrate so that the color filters will be opposed to the pixelelectrodes 110 formed in the TFT substrate 1. At this time, the colorfilters 202 are associated with red, green, and blue respectively thatare an example of a set of different colors, and formed as color filters202R, 202G, and 202B respectively. The color filters 202R, 202G, and202B may be, as shown in FIG. 8, separated from one another by a blackmatrix 203. A protective film 204 and an alignment film 205 are formedover the color filters 202 and black matrix 203. A transparent electrode206 and the sheet polarizer 7, for example, are formed on the back ofthe color filter substrate 2, that is, the side of the transparentsubstrate 201 opposite to the side thereof on which the color filters202 are formed. At this time, the sheet polarizer 7 formed on the colorfilter substrate 2 is paired with the sheet polarizer 6 formed on theTFT substrate 1.

In a display device that uses three primary colors of red, green, andblue to achieve color display, a set of a red pixel, a green pixel, anda blue pixel constitutes one display pixel. Various colors can bereproduced by controlling gray levels to be produced at the respectivepixels.

In the TFT substrate 1 shown in FIG. 5, the color temperature can becontrolled by disposing a metallic pattern 104 b, which serves as afield through which light is not emitted, at each of pixels associatedwith a specific color (red pixels). Since the metallic pattern 104 bserves as the field through which light is not emitted, it is an invalidfield as it is. The metallic pattern 104 b is therefore disposed at acorner of each pixel zone, and the pixel electrode 110 is recessed alongthe field of the metallic pattern 104 b. Consequently, when a bridgingconnection 112 that will be described later is applied to the field, theirregularity in a luminance can be reduced without influence on anaperture ratio.

Moreover, the common electrodes 103 included in each red pixel, eachgreen pixel, and each blue pixel respectively juxtaposed laterally onthe page of FIG. 5 are, as shown in FIG. 5 and FIG. 7, connected to thecommon signal line 104 a and thus used in common.

Moreover, as shown in FIG. 5 and FIG. 7, only the common electrode 103included in each red pixel is electrically connected to the commonelectrodes 103 included in other red pixels, which are juxtaposedvertically on the page of FIG. 5 to the red pixel, using the respectivebridging connections 112 formed in the same layer as the layer in whichthe pixel electrodes 110 are formed. For this purpose, each red pixelincludes the metallic pattern (electrode pad) 104 b that is connected tothe bridging connection 112 by way of a through hole and also connectedto the common electrode 103. As mentioned above, the common electrodes103 included in the respective red pixels juxtaposed vertically on thepage are connected using the bridging connections 112. Consequently, notonly a voltage applied to the common electrodes 103 included in therespective pixels juxtaposed laterally on the page of the drawing isstabilized but also a voltage applied to the common electrodes 103included in the respective pixels juxtaposed vertically therein isstabilized.

FIG. 9 is a plan view showing an example of a display device in whichthe TFT substrate 1 shown in FIG. 5 is employed, wherein the displaydevice is seen from the side of the color filter substrate 2. 202Rdenotes a field in which a red color filter is formed, 202G denotes afield in which a green color filter is formed, and 202B denotes a fieldin which a blue color filter is formed. 203 denotes an interceptive film(black matrix) that has openings aligned with respective pixels. Theedges of the interceptive film and the edges of the color filters aresuperimposed on one another. 113 denotes a field within a red pixel zonethrough which light passes, 114 denotes a field within a green pixelzone through which light passes, and 115 denotes a field within a bluepixel zone through which light passes.

In the display device, as shown in FIG. 9, the area of the field 113within the red pixel zone through which light passes is smaller than thearea of the field 114 within the green pixel zone through which lightpasses and the area of the field 115 within the blue pixel zone throughwhich light passes.

Moreover, at each pixel in the TFT substrate 1, as shown in FIG. 5 andFIG. 8, the pixel electrode 110 is layered over the common electrode103, for example. On a planar basis, the pixel electrode 110 and thecommon electrode 103 that are planar are superimposed on each other.Consequently, a capacitive device is realized by the common electrode103, first insulating film 105, second insulating film 109, and pixelelectrode 110.

In the example shown in FIG. 5, the area within the outer margin of thepixel electrode 110 disposed at each red pixel is smaller than that ateach blue or green pixel. Since the pixel electrode 110 at the red pixelis different from that at the green or blue pixel, a capacitance offeredat the red pixel differs from that offered at the green or blue pixel. Avoltage to be applied to each pixel electrode 110 via a TFT differs froma voltage to be applied to other pixel electrode. If the way the voltagedifference is generated differs from pixel to pixel, an optimal voltageof a common electrode differs from pixel to pixel. Consequently, anafterimage or smear is likely to occur. Therefore, the slits or openingsare formed in the pixel electrode 110 at each pixel so that thedifferences in the area of the pixel electrode among the red, green, andblue pixels can be approximated to one another. In this way, thedifference of the capacitance offered at each red pixel from thecapacitance offered at each green or blue pixel can be decreased.

For example, as shown in FIG. 5, the area occupied by the slits 110 s oropenings formed at each red pixel (specific pixel at which the metallicpattern is disposed) is made smaller than the area occupied thereby ateach of the other pixels. An area by which the pixel electrode 110 andcommon electrode 103 are superimposed on each other is calculated bysubtracting the area occupied by the slits 110 s or openings from thearea defined by the outer margin of each pixel zone.

In FIG. 5, the lengths of slits 110 s formed in the center of the pixelelectrode disposed at each red pixel (specific pixel having the metallicpattern 104 b disposed thereat) are different from those of slits formedin the center of the pixel electrode disposed at each of the otherpixels. The center of the pixel electrode at each pixel is a field whereslits oriented in different directions coexist. By adjusting the lengthsof the slits 110 s formed in the center of the pixel electrode at eachpixel, an invalid field is decreased and the pixel can be effectivelyutilized.

FIG. 10 to FIG. 14 are illustrative explanatory diagrams concerningother ideas of forming slits in a pixel electrode. Since slits formed ateach green pixel may have the same pattern as slits formed at each bluepixel do, FIG. 10 to FIG. 14 do not show the blue pixel. FIG. 10 is aplan view showing a case where the positions of slits in each pixelelectrode are identical between the red pixel and the green or bluepixel. FIG. 11 is a plan view showing a case where the number of slitsin each pixel electrode is different between the red pixel and the greenor blue pixel. FIG. 12 is a plan view showing a case where the angle ofslits in each pixel electrode is different between the red pixel and thegreen or blue pixel. FIG. 13 is a plan view showing a case where some ofslits in each pixel electrode are left open. FIG. 14 is a partiallyenlarged plan view showing the case shown in FIG. 13.

The structure disclosed using FIG. 5 has constituent features describedbelow.

-   -   (A) An aperture ratio of each red pixel is smaller than an        aperture ratio of each of the other pixels, that is, the green        or blue pixel.    -   (B) A total area occupied by the slits 110 s in the pixel        electrode 110 at each red pixel is smaller than a total area        occupied by the slits 110 s in the pixel electrode 110 at the        green or blue pixel.

In the display device according to the first embodiment, as long as theabove two conditions (A) and (B) are satisfied, the shape of the slits110 s may be selected from among various shapes other than the one shownin FIG. 5.

For example, as shown in FIG. 10, the positions of the slits 110 s inthe pixel electrode at each pixel may be the same between the red pixeland the green or blue pixel, but the slits 110 s formed at the upper andlower ends of the pixel electrode 110 at each green pixel may be longerthan the slits 110 s formed at the upper and lower ends of the pixelelectrode 110 at each red pixel.

For example, as shown in FIG. 11, the positions of the slits 110 s inthe pixel electrode 110 at each green pixel may be shifted, and thenumber of slits 110 s in the pixel electrode 110 at the green pixel maybe larger than the number of slits 110 s in the pixel electrode 110 ateach red pixel. In the case shown in FIG. 11, the number of slits 110 sin the pixel electrode 110 at each red pixel is nineteen, and the numberof slits 110 s in the pixel electrode at each green pixel is twenty.

For example, as shown in FIG. 12, the angle θ_(G) of the slits 110 s inthe pixel electrode 110 at each green pixel may be larger than the angleθ_(R) of the slits 110 s in the pixel electrode 110 at each red pixel.In this case, for example, in the center of the pixel electrode at eachpixel in which the slits oriented in the first direction and the slitsoriented in the second direction face each other, an invalid field inthe pixel electrode at each green pixel is smaller. Consequently, theaperture ratio of each green pixel becomes larger than the apertureratio of each red pixel.

Moreover, for example, the spacing between adjoining ones of the slits110 s in the pixel electrode 110 at each green pixel may be narrowerthan the spacing between adjoining ones of the slits 110 s in the pixelelectrode 110 at each red pixel. Moreover, the width of the slits 110 sin the pixel electrode 110 at each green pixel may be larger than thewidth of the slits 110 s in the pixel electrode 110 at each red pixel.

Moreover, the slits 110 s formed in the center of the pixel electrode110 at each pixel in which the slits oriented in the first direction andthe slits oriented in the second direction face each other may have, asshown in FIG. 13 and FIG. 14, one ends thereof merged into the edge ofthe pixel electrode 110 and left open. When the slits 110 s are leftopen, an invalid field decreases accordingly. Consequently, the apertureratio of each pixel rises. Moreover, since the slits 110 s formed in thefield where the slits oriented in the first direction and the slitsoriented in the second direction face each other are left open, if theupper or lower half of the pixel electrode 110 becomes defective asshown in FIG. 14, a portion indicated with a dashed line in FIG. 14should merely be cut out. Thus, the pixel electrode 110 can be dividedinto two upper and lower portions. This facilitates repair of a defect.

The advantage that a defect can be repaired readily is provided by thestructure that the pixel electrode 110 includes a first field in whichslits are oriented in a first direction, a second field in which slitsare oriented in a second direction, and a third field which isinterposed between the first and second portions and in which the slitsoriented in the first direction and the slits oriented in the seconddirection face each other. In the third field, one ends of the slits areleft open.

Second Embodiment

FIG. 15 and FIG. 16 are illustrative plan views showing other examplesof structures different from the ones shown in FIG. 5 and FIG. 9respectively.

In the first embodiment, for example, as shown in FIG. 5, only thecommon electrode 103 included in each red pixel is connected to thecommon electrode 103 included in other red pixel using abridgingconnection 112. Thus, the aperture ratio of, each green or blue pixel islarger than the aperture ratio of each red pixel. The present inventionis not limited to this mode. Alternatively, the width of one of thethree kinds of pixels may be changed from the width of the other kindsof pixels in order to make the aperture ratio of each green or bluepixel larger than the aperture ratio of each red pixel. In the secondembodiment, the width of each red pixel is smaller than the width ofeach green or blue pixel so that the aperture ratio of the green or bluepixel will be larger than the aperture ratio of the red pixel.

In the TFT substrate 1 included in a liquid crystal display device inaccordance with the second embodiment, as shown in FIG. 15, the spacingDPR between drain lines 107 on both the sides of each red pixel isnarrower than the spacing DPG or DPB between drain lines 107 on both thesides of each green or blue pixel. In this case, the common electrodes103 included in the three kinds of pixels respectively may be connectedto the common electrodes 103 included in the three kinds of pixelslocated vertically adjacently using the respective bridging connections112.

FIG. 16 is a plan view showing the liquid crystal display device shownin FIG. 15 from the side of the color filter substrate. The area 113 ofa field within each red pixel zone through which light passes is smallerthan the area of a field 114 or 115 within each green or blue pixel zonethrough which light passes. In other words, in the liquid crystaldisplay device according to the second embodiment, the aperture ratio ofeach red pixel is smaller than the aperture ratio of each green or bluepixel. Consequently, the color temperature can be controlled in the samemanner as that in the first embodiment.

In the liquid crystal display device according to the second embodiment,for example, the slits 110 s are formed in the pixel electrode 110disposed at each pixel in order to improve a viewing angle. When theslits 110 s are formed in the pixel electrode, for example, as shown inFIG. 15, the positions of the slits at each red pixel should bedifferent from the positions of the slits at each green or blue pixel.Thus, an invalid field at each red pixel and an invalid field at eachgreen or blue pixel can be reduced. In FIG. 15, the orientation of theslits at each pixel is different between the upper and lower halves ofthe pixel. The present invention is not limited to this mode. The slitsmay be oriented in the same direction.

FIG. 17 and FIG. 18 are illustrative explanatory diagrams showingvariants in which the slits in a pixel electrode are different fromthose adopted in the liquid crystal display device in accordance withthe second embodiment. FIG. 17 is a plan view showing slits havingdifferent spacings, and FIG. 18 is a plan view showing slits havingdifferent thicknesses.

Even in the second embodiment, similarly to the first embodiment, atotal area occupied by the slits 110 s in the pixel electrode 110 ateach red pixel is smaller than a total area occupied by the slits 110 sin the pixel electrode 110 at each green or blue pixel. Thus,differences in a capacitance produced between the common electrode andthe pixel electrode occurring among three kinds of pixels are minimized.

Consequently, even in the liquid crystal display panel included in thesecond embodiment, an area occupied by slits formed at each pixel whoseaperture ratio is small is smaller than an area occupied by slits formedat each pixel whose aperture ratio is large. As long as this conditionis satisfied, the slits 110 s in the pixel electrode 110 at each redpixel may have any relationship to the slits 110 s in the pixelelectrode 110 at each green or blue pixel. For example, the positions ofthe slits 110 s in the pixel electrode may be the same between the redpixel and the green or blue pixel, but the uppermost and lowermost slits110 s in the pixel electrode 110 at each green pixel may be longer thanthe uppermost and lowermost slits 110 s in the pixel electrode 110 ateach red pixel.

For example, as described in relation to the first embodiment, thepositions of the slits 110 s in the pixel electrode 110 at each greenpixel may be shifted so that the number of slits 110 s in the pixelelectrode 110 at the green pixel will be larger than the number of slits110 s in the pixel electrode 110 at each red pixel.

Otherwise, for example, as described in relation to the firstembodiment, the angle θ_(G) of the slits 110 s in the pixel electrode ateach green pixel may be larger than the angle θ_(R) of the slits 110 sin the pixel electrode at each red pixel. In this case, an invalid fieldin the center of the pixel electrode 110 at each green pixel in whichthe slits oriented in the first direction and the slits oriented in thesecond direction face each other gets narrower. Consequently, theaperture ratio of each green pixel becomes larger than the apertureratio of each red pixel.

For example, as shown in FIG. 17, the spacing SGG between adjoining onesof the slits 110 s in the pixel electrode 110 at each green pixel may benarrower than the spacing SGR between adjoining ones of the slits 110 sin the pixel electrode 110 at each red pixel. Moreover, as shown in FIG.18, the thickness (width) SWG of the slits 110 s in the pixel electrode110 at each green pixel may be larger than the thickness (width) SWR ofthe slits 110 s in the pixel electrode 110 at each red pixel.

The slits formed in the center of the pixel electrode 110 at each pixelin which the slits oriented in the first direction and the slitsoriented in the second direction face each other may, as shown in FIG.13 and FIG. 14, have one ends thereof merged into the edge of the pixelelectrode 110 and left open. When the slits are thus left open, aninvalid field decreases accordingly. Consequently, the aperture ratio ofeach pixel improves. At this time, when the slits formed in the fieldwhere the slits oriented in the first direction and the slits orientedin the second direction face each other are left open, if the upper orlower half of the pixel electrode 110 becomes, for example, defective,the pixel electrode can be separated into two portions by merely cuttingout one portion as shown in FIG. 14.

In the second embodiment, the common electrodes included in each redpixel, each green pixel, and each blue pixel respectively are connectedto the common electrodes 103, which are included in pixels locatedvertically adjacently, using the respective bridging connections 112.The present invention is not limited to this mode. Alternatively, onlythe common electrode 103 included in each red, green, or blue pixel maybe connected to the common electrodes included in pixels locatedvertically adjacently.

Moreover, the aperture ratios of three kinds of pixels of red, green,and blue pixels may be different from one another, though thisconstituent feature is not illustrated.

The present invention has been concretely described based on theembodiments. Noted is that the present invention will not be limited tothe embodiments but can be modified in various manners without adeparture from the gist of the invention.

1. A liquid crystal display device in which: first color filters formedin openings bored in a black matrix, second color filters formed inopenings bored in the black matrix, and third color filters formed inopenings bored in the black matrix are included in a first substrate;first, second, and third pixel electrodes are formed in association withthe respective color filters in a second substrate opposed to the firstsubstrate with a liquid crystal therebetween; common electrodes areformed on a planar basis to be superimposed on the respective pixelelectrodes with an insulating film therebetween; a plurality of slits isformed in each of the pixel electrodes; and the liquid crystal iscontrolled with electric fields induced by each of the pixel electrodesand each of the common electrodes in order to produce an image, wherein:the common electrode corresponding to a specific pixel electrode out ofthe first, second, and third pixel electrodes is electrically connectedto the common electrodes corresponding to respective adjoining pixelelectrodes using respective bridging connections; and the area of thespecific pixel electrode defined by the outer margin thereof is smallerthan the area of each of the other pixel electrodes defined by the outermargin thereof.
 2. A liquid crystal display device in which: first colorfilters formed in openings bored in a black matrix, second color filtersformed in openings bored in the black matrix, and third color filtersformed in openings bored in the black matrix are included in a firstsubstrate; first, second, and third pixel electrodes are formed inassociation with the respective color filters in a second substrateopposed to the first substrate with a liquid crystal therebetween;common electrodes are formed on a planar basis to be superimposed on therespective pixel electrodes with an insulating film therebetween; aplurality of slits is formed in each of the pixel electrodes; and theliquid crystal is controlled with electric fields induced by each of thepixel electrodes and each of the common electrodes in order to producean image, wherein: the common electrode corresponding to a specificpixel electrode out of the first, second, and third pixel electrodes iselectrically connected to the common electrodes corresponding torespective adjoining pixel electrodes using respective bridgingconnections; and the common electrode associated with each of the pixelelectrodes other than the specific pixel electrode is not connected tothe common electrodes corresponding to respective adjoining pixelelectrodes using the respective bridging connections.